Technical Abstract:
We developed a process, the Vacuum/Steam/Vacuum (VSV) process, which kills bacteria in the surface of solid foods. It is a rapid process and should be able to keep up with typical line speed in a process plant. Typical treatment times are 1 ' 2 s. The primary goal was to develop a process to kill bacteria on chicken with no thermal damage. The process involves removing the air and water film barriers on the surface so saturated steam can make intimate contact with the bacteria. Vacuum removes these films. Steam then kills the bacteria. A final vacuum step evaporatively cools the product surface, hence the process name - VSV. Because the saturated steam condenses on contact depositing a new film of water, cycling between vacuum and steam improves the process. The ideal process would kill up to 5 log bacteria on chicken. However, chicken presented many difficulties. It is wet from upstream processing. It has numerous 'hiding places' such as under the wings, under the legs, in the skin folds especially at the top and bottom. The worst hiding place is in the visceral cavity. Chicken carcasses are also very susceptible to both thermal and mechanical damage. The skin and meat readily reveal thermal damage and the carcasses rip easily. In spite of these obstacles, we developed a process that kills 1 ' 1.5 log of bacteria with little or no thermal damage and no mechanical damage. The research was a technical success but industry is not knocking down the doors because of the relatively low bacteria kill and high initial capital cost. However, along the way, we developed the VSV process for various other foods, most notably hot dogs. We were able to achieve up to 5 log kill of surrogate bacteria on hot dogs. As a result of this spin-off, we entered into a Cooperative Research and Development Agreement with industry to commercialize the process. Commercialization is imminent.